Montserrat Volcano Observatory

Daily Report
Report for the period 16.00 17 May
to 16:00 18 May 1997
The current alert level is ORANGE

Volcanic activity continued at a high level during the last 24 hours, with small pyroclastic flows from the north of the dome, and two swarms of hybrid earthquakes. The northern side of the crater has filled up, and a very small amount of dome material has fallen into the top of White's Ghaut.

The dome has been clear of cloud for most of the day, which has allowed a partial survey of the dome from the helicopter. The most active area was the northern side, with small pyroclastic flows travelled to the edge of the crater and then being diverted down the Tar River valley to where the Tar River soufriere used to be. This activity has resulted in the crater filling in, so that the dome is now flush with the low notch in the crater wall at the top of White's Ghaut, and a few small boulders have fallen into the top of the ghaut. During helicopter flights this morning, an area of intense steam and ash venting was seen near the top of the dome, which was intermittently throwing out fist to head sized fragments into the air. This suggests that there is high gas pressure within the dome.

The first hybrid earthquake swarm started at 4:10 pm yesterday and lasted until 7:25 pm. This was followed at around 8 pm by a period of dome collapse, with small pyroclastic flows to the north and north-east. The earthquake swarm and pyroclastic flows were not as large as the episodes yesterday morning, and the level of activity declined at 8:30 pm.

Another hybrid earthquake swarm began at 4:02 am, and lasted until 7:04 am. This was followed by another collapse between 8:20 am and 9:30 am, with several small pyroclastic flows into the Tar River valley. Since then the volcano has been quieter, with a few small pyroclastic flows. There were a total of 43 hybrid and 23 long-period earthquakes. Ninety rockfall signals were also recorded, an increase since yesterday.

Views of the dome were possible throughout the night, with intense glowing seen on the northern side. Several small pyroclastic flows were witnessed from Harris and Whites.

A further attempt was made to see the new EDM targets from Farrell's but they could not be seen. A further visit to the crater rim is required to re-position the reflectors.

Observations made today suggest that the volcano is in a dangerous phase, and there are signs that the gas pressure within the dome is high. In addition, the current area of growth is threatening the northern flanks of the volcano, in particular the White's and Tuitt's Ghauts. The Tar River valley, Long Ground, White's and Tuitt's areas are very dangerous, and should not be entered, as pyroclastic flows in all these areas are now possible. Nobody should enter zones A and B, and only essential visits should be made to the evacuated zone. Ash masks should be worn when in the ashy areas.

Dr Anne-Marie Lejeune left MVO today for a short visit to France. She will be back at the end of the week.

Montserrat Volcano Observatory